This proposal requests funds for the purchase of a VG Instruments TRIO-2 Liquid Chromatograph/Mass Spectrometer (LC/MS) system for the SUNY-Stony Brook Mass Spectrometer Facility. LC/MS will significantly promote the research objectives and laboratory productivity of eleven distinguished scientists who comprise the major users group. This mass spectrometer system will make directly available to these investigators important new techniques for the structural analysis of molecules which are presently unavailable at SUNY-Stony Brook and inaccessible or difficult to obtain from other organizations. LC/MS is unsurpassed for the analysis of a variety of molecules with a profound biomedical importance, including compounds which are non-volatile, labile, or thermally unstable; are charged or zwitterionic in solution; or are small biopolymers of amino acids, deoxynucleotides, or sugars. Techniques for coupling a liquid chromatograph to a mass spectrometer (thermospray, particle beam, electrospray ionization, and atmospheric pressure ionization) now permit the routine analysis of these substances with the ease and rapidity that GC/MS has provided for volatile samples in the past. The instrument will be operated and maintained by trained personnel, and an advisory committee will ensure access to all PHS-supported investigators and be responsible for the long term operation of the instrument.